Transcript Introduction to Active Galactic Nuclei (2013년 6월 세종대학교)

활동성 은하의 소개
세종대학교
천문우주학과
이희원
Active Galactic Nuclei
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Compact Nuclear Region
Nonthermal Spectrum
Prominent Emission Lines
Broad Permission Lines (5000 km/s)
Narrow Forbidden Lines (500 km/s)
Significant Variability
Seyferft 은하, 전파 은하
QSO, Quasar
Blazar, LINER
Classification of AGN
1. Classification according to radio
property and luminosity
M <-23
M>-23
Radio-Loud Quasar
Radio Galaxy
Radio-Quiet QSO
Seyfert Galaxy
Energy and Time Scales
• 10^12 solar luminosity: 보통 은하보다 훨
씬 더 밝다.
• 수 일 이하의 변광: 태양계 보다 좁은 지역
에서 에너지 생성.
• 거대 블랙홀의 질량이 태양의 수십억배에
이를 수 있다.
• Reverberation mapping
Reverberation Mapping
• 연속선 복사 세기
와 방출선 복사 세
기 변화를 추적 관
측 (시계열 관측)
Classification according to Line Spectra
• Type 1 AGN
-Exhibit Both Broad and Narrow
Lines
-Type I Seyfert Galaxy
-Broad Line Radio Galaxy
• Type 2 AGN
-Exhibit Only Narrow Lines
-Type 2 Seyfert Galaxy
-Narrow Line Radio Galaxy
#Broad Absorption Line Quasar
#Type 2 Quasar
AGN Spectra (W. Keel)
Type II AGN
• Seyfert galaxies : Type I and Type II
Type 2 Quasar
Spectrum of Type 2 Quasar
Line Emitting Regions of AGN
• Broad Emission Line
Region
-Located <0.1 pc
-High density
• Narrow Emission Line
Region
-Extended to 100 pc
-Low density
#Reverberation Mapping
Spectropolarimetry of Seyfert Galaxies
• Hidden broad emission line photons can
be observed in the scattered spectra that
are characterized by strong polarization
• Spectropolarimetry of NGC 1068 by
Miller Goodrich & Mathews (1991)
- Polarized Broad Hβ
- Unpolarized Narrow [O III] 4959, 5007
• Electron Scattering
-Uniform polarization degree and position
angle
Spectropolarimetry of NGC 1068
Various Looks of NGC 1068
Polarization of Scattered Radiation
• Electromagnetic waves
are transverse waves with
oscillating electric and
magnetic fields
• The electric field direction
characterizes the
polarization of light
• When a photon is
scattered, polarization
develops in the direction
perpendicular to the
scattering plane
• P= sin2θ/1+cos2θ
The Narrow Line Radio Galaxy Cyg A
Spectropolarimetry of Cyg A
Spectropolarimetry of Broad Line Radio
Galaxies
Polarimetry provides a
natural mirror
allowing views of
hidden regions
Broad Absorption Line Quasars
• Exhibit P Cyg type
Profiles in Broad
Permitted Lines
• 10 percent of RadioQuiet Quasars
• Outflowing wind
velocity ~0.2 c
• Radiatively driven
wind : Line-locking
Phenomena in Ly a
1216+NV 1240
Spectropolarimetry of BAL Quasar
Quasar Absorption Systems
• 퀘이사는 은하간 공간의 배경 광원의 역할을 한
다.
• 은하간 공간에 존재하는 물질들이 퀘이사 빛을
흡수하므로, 이들의 존재를 알 수 있다.
Quasar Absorption Systems
• Lyman Alpha Forest
• Lyman Limit System
• Damped Lyman Alpha System
Lyman alpha forest
• Residual neutral hydrogen component forming a
filamentary structure in the intergalactic medium
• Appears in the absorption profile blueward of
Lyman alpha of a background quasar
Damped Lyman Alpha Systems
• Defined by N_HI>2X10^20
cm^-2
• Maybe disk component of
a galaxy intervening the
sightline
• Contain most neutral
hydrogen providing raw
material for star formation
during the most of the
cosmic time from the
reionization era.
• Important probe for
cosmic chemical evolution
• May contain some dust.
Chemical
Evolution with
DLAs
Voigt Profile
• Convolution of a Gaussian and
a Lorentzian
• The core part is approximately
Gaussian whereas the wing
part is Lorentzian.
• Resonance line shape is
approximately Lorentzian in
the near wing part.
• Far wing part, deviation from a
Lorentzian is observed
depending on the atomic
wavefunction.